Among 18 necropsy patients aged 15-52 years (mean 34) with the Marfan syndrome, 13 had fusiform aneurysms of the sinus and proximal tubular portions of ascending aorta, severe aortic regurgitation (AR) and severe aortic medical degeneration; three had dissection involving the entire aorta which was not dilated previously and the aortic media was normal histologically, and two patients had isolated mitral regurgitation with grossly and histologically normal aortas. Of the nine with fusiform ascending aortic aneurysms, two reptured spontaneously; of the remaining 11, nine died after operations to correct the severe AR. Of the three with aortic dissection, two had systemic hypertension before the dissection. Although the only cardiovascular manifestation of the marfan syndrome was MR in two patients, seven of the other 16 patients also has clinical evidence of MR and 11 of the total 18 had anatomic mitral abnormalities including dilated (more than 11 cm) anuli (11 patients), prolapse (7 patients), ruptured chordae tendineae (5 patients) and mitral anular calcium (5 patients).